First autos dying

These are my first autos that I’ve grown and I have some sort of problem, the 2 that are messing up are candy avalanche and they are about 4 weeks into flower, I didn’t have any problems during veg. I’m using promix organic garden mix with added perlite, FF trio of nutes (I’m out of big bloom) and a 600 watt hps light. The problem started right after they started flowering. I was using distilled water but I switched to tap water that has been setting out for 24hrs for the calcium because I don’t have any cal mag. I flushed them the other day because I thought maybe there was a buildup of salts and watered the next day with 1/2 strength nutes, but they aren’t getting any better.

Have you checked the ph of your tap water? And the runoff?

Looks like deficiencies to me. You said you are out of calmag so you can start there. Could be locked out too so check your ph and runoff as suggested above. After you flush pay attention to the new growth. The damaged leafs may never recover.