generally after a phosphorus deficiency has been corrected the leaves that have been badly affected will dry up and die....its normal nothing you can do about it....learn from it...are you using hardwater ...tap water .. or distilled water??
i can tell you from personal experience that ....ph problems definetly led to other defiencies with your imobile trace elements...iron ..magneseum...calcium....etc. something to keep in mind
a thing to remember in hydro..is your micro life that are usually abundant in soil setups....are not so abundant on their own in hydro setups.....Big Bloom is awesome for replenishing your micro environment after a good flush.......mixed with some stuff called Liquid Karma...Botanicare.
sorry that last post was meant for someone else....drain to waste systems are a lot easier to manage..do you have a airstone in the resevoir?????that will help with the algae growing also is the resevoir covered...light and heat will cause growth...well humidity as well.
what kinda of set-up are you running???are you using organics or syn's???did you flush with a mild-nutrient solution or did you not put nuts in the water at all???you said the ph is 5.7....i will assume your using a recirculating hydro set-up...ebb and flow???if this is the case when you flush...