[SuiJuris]

OK thanks for the advice.

My soil mix has no addiditives (eg dolomite lime, bonemeal etc) in it, is this OK? If not then why do people add these kinds of additives?

- Soil additives such as these (such as lime) are for increasing or decreasing ph levels. you will have to do some research yourself on adding these. a good mix is 2/3 soil to 1/3 perlite, it has worked for me, dont get crazy into soil mixes on your first grow. so to answer, i think youll be fine just as you are.

So I am not supposed to be washing through every time then fertilising every water. It will not take long for salt build ups to occurr if I am fertilising every water - I guess?

- according to your post you were watering every 3 days, this is alot, on top of this you are fertilizing every watering. This is alot of fertilizer, i would stop. your soil mix has plenty of nutrients in it to take care of your plant for a while in the first place, and like i said many people only fertilize only a few times during the whole cycle of growth. stop watering ever three days, to check if it needs watering, stick your finger in the soil about 1 - 2 inches down, if it feels dry, ad enough water to evenly moisten the soil thoroughly, so that it has the feel of a wringed out sponge, overwatering causes problems, try this from now on.

Perhaps there could be too much salt in the medium which is preventing the roots from absorbing Potassium. Which could be why I kept getting burned tips and edges because the leaves couldnt transpire as much water? But since I was washing-through each time surely that would remove these salt build-ups.

- It does sound like you have fertilizer burn, too much nitrogen, adding the over watering and because of exsessive water you probably have poor soil aeration (compaction of the soil)... transpiration allows built up toxins to be released through the stomata on the underside of the leaves. you can aid this by putting a fan on your plants. i do not think the cause is related to inadequate transpiration.

Are there disadvantages of washing the plant through? Maybe disturning root system?

- it can disturb the root system when you excessisvely wash it through, as well as the other aformentioned results.
there is a time for doing so, such as when you have salt buildups (over fertilizing)

Does my 3 day watering cycle sound about right for these pots and light and size of plants? Any suggestion about a fertiliser schedule?

- A good fertilizing schedule is the one posted on your fertilizer ;-) seriously though.
remember, you need not fert every watering, and really you should not worry too much about a yellow leaf and or a brown spot here or there (for future reference)... its just not practical to try and fix every little imperfection, as well as being close to impossible. try some of the things i suggest and see where that gets you.

The temperature I can not do anything about can keep it stable during the day at 80 degrees. Will this be OK is there a lot more chance of getting funghi attacks? Are there any problems with growth at these temperatures? It is just not possible for me to fit an extraction unit there.

- This has been answered already...good response too. so i think i will go grab me a cup a coffee now, take care, and cut back the water and fert!.

Ave.