Plants a light green color

have you giving them any nutes?

 

You could try mixing some grow nutrient solution and throw it in a spray bottle and foliar feed them (aim for pH 6). This allows you to let your soil dry out a bit and still gets nutrients to the plants. In case you don't know, leaves absorb best through the bottom so spray from underneath.

 

Get the pH of the water you're using right before you give it and you don't have to worry about the runoff pH. The soil pH should be at 7 which is neutral for soil. But don't try to measure the pH by the runoff water. I suspect your plants are yellowing because of the nutes that are in the FFOF soil. If you've flushed them already then you just flushed out all the nutrients that were in the soil and now you'll be completely responsible for all feeding of these plants until they get repotted into fresh soil. You need to get a good understanding of the watering process right now before you do any major damage to them. Do not water your plants until they are at least 80% dry. Actually, they should feel as light as they did when you first loaded the pot with fresh soil before you put your clone in. These plants require defined wet/dry cycles to stay healthy. The roots do not like sitting around in moist conditions constantly. So do not water until the plant actually needs it if you want to keep them healthy. The pH of the water you give your plants is a BIG DEAL. The range for soil is 6.3 to 6.7 and you've got to get it within that range if you don't want the roots of your plants to lock up. Cheap pH testers are worthless and not dependable. If you want a tester stick to use that you can actually depend on for a true reading, you're going to have to lay down some bucks for it. I bought one of those cheap pH testers once and almost lost my whole room full that cycle. I found out several weeks down the road that the readings it had been giving me were wrong from the very start. You can get a decent one for $60+ and the gold standard is BlueLab and theirs costs around $100. The pH range is something so very important that it's worth it to have something you can depend on in my opinion.
During veg, if you use the correct soil, understand how to water properly and adjust the pH of the water you use to the correct range, the veg cycle should be a breeze. Go ahead and use tap water for your plants. You don't have to let it sit for 24 hours because they don't treat water with chlorine anymore. They switched to chloramine which doesn't evaporate nor is there enough of it in the water to damage your plants. But you've got to adjust any liquids going into your plants to the correct pH range. You shouldn't need to give any nutes until a few weeks into the veg cycle. Nutes are intended to be used only after the plant has had the opportunity to use up what naturally came in the soil. We typically don't have to give ours nutes until near the end of the veg cycle and then they get them throughout the flower cycle.
There are lots of great threads in the new growers section here on the forum. Several posts are just for new inexperienced growers and provide the very basics that one needs to know to be successful when first starting out. The more you know, the easier time you'll have. Information is most definitely your friend when first starting out with the hobby. Good luck! TWW

 

Where I live, from what I've been able to determine because I myself wanted to know, we still use chlorine. Metro Vancouver, BC, So don't assume your municipality has switched. Do a little digging and you can find out for yourself which is true.