Me and My Girls need Help!

I am in my 4th week on a grow of NL's and I have been chasing a problem that started out as a few rust spots on a couple leaves on one of four plants in a Eco Grower Hydro/DWC/Drip system. The spots are now on a couple of other leaves but only a few. I could give you a history of all the steps I've taken but at this point I figured to give the experts a few basics to generate comments and questions (for some reason I cant upload Pics). PH has averaged 5.3 with little swings; HG Flora Series @ PPM 720 (.50 Hanna); Solution Temp 72F; Tent Temp 79F & 55% RH during Day & 69F & 40% RH during night time. I can provide additional info as requested. Thanks

Running ph that low in soiless can give you problems with cal/mag uptake.Try 5.8 to 6.0

Rust spots can be caused by a parasite and may be serious. I would, if practical remove all effected leaves. If you finish this grow sterilize the grow-op before proceding and get rid of any infected plants.

A PH swing between 5.5 and/to 6.3 are maximum outside ranges for hydro. 5.8PH for hydro.

It is better to swap out the res every 5-7 days than to re-PH and add more fertilizer.

Have you tried upping you ph to like 5.8. I don't do hydro etc but isn't 5.3 the lower end of the scale. Also what is your medium and water temps is 72?

Ph should be 5.8 to 6.0 otherwise you will have calcium and magnesium uptake problems.

How do your roots look? 5.3 is a little low if you ask me. That is at the low end of Ca uptake, and rust colored spots are a sign of calcium def. Also, are you using ro water, or tap water? What is the ec prior to adding nutes? If you are using ro water, I would use Calmag, to help with your calcium def. Also, at 72 deg water, are you using a sterilizing agent or beneficial to keep root rot under control?