My babies are turning brown at the tips. Flushing question.

[ol'overgrower]

My sativa plant's leaves are browning at the tip and curling upward. This more than likely means nute burn so I'm definately considering flushing them today. However, it came a freakin flood a few days ago and my soil is very moist already. I don't think the soil has had a chance to dry for over a week now. Would it be ok to go ahead and do the flush and risk overwatering? The question I guess is what is the lesser of two evils: overwatering or waiting a few days for the soil to dry while risking further damage by the nutes?

Here's my grow info:

I have two plants growing right now. One indica and one sativa, both are about 28-30 days old, 5-6 inches high and are growing the 5th node.
They are in 1.5 gallon pots with mixed soil. Mix is simply 1/3 dirt that came from an abandoned stable for cows basically 20 year old cow shit, and a little less than two thirds topsoil that I dug up from a really wet area in the woods behind my house. I also added a little sand and MG potting soil with perlite for drainage. I've been using MG all purpose about once a week for fert.
I know it sounds like I'm half assing this but I sort of have no money to spend a.t.m. and am thinking this will feed the plants adequetly. They have been doing great and thriving so far. The first problem I had, and up til now the only problem, was that the insects loved my indica way too much but never even touched the sativa. I fixed this by spraying them once or twice a week, depending on rain, with fungicide 3 garden safe which is for mites, insects, and fungus.

[FlowerGirl]

As the soil dries the toxic salt buildup from the nutes gets more concentrated.
flush them now. Your ferts will work fine as long as you are using the right one for veg. whats the NPK% ?

[ol'overgrower]

15-30-15