Sulfer deficiency confirm/deny?

Pretty sure I it's sulfur def. Which is weird cause I'm using foxfarms (just took out grow big as I am going into flower) Been experiencing this issue on my three smaller, the fourth is a bit bigger and going great with no symptoms.

Sorry about the hps pics it's all I can get at the moment

Maybe I should flush them? Or add Epsom salt?

no dont think so. add cal-mag for micro nutrients it should solve your prob.
Looks more like magnesium def

Sulfur is mobile. That means if it was a sulfur deficiency the plant would be pulling it from the lower part of the plant and moving it to new growth. So the sicker leaves would be down low.

What is it exactly that makes you think the plant is sick? The stems look reddish, there's a bit of tip burn, but other than that the plant doesn't look horrible to me. The newest growth looks a little yellowish but that could be the lighting...

How big are the plants in relation to the pots?