Howdy Evan,
Can I ask what nutrients you're using and what strains you're growing??
I feed my autos at exactly the same strength as my photo ladies and I really struggle to burn them at all. I use the
BioBizz range btw. I can only just start getting tip burn when my feed is 4ml grow, 4ml bloom, 4ml topmax & 2ml cal/mag. Perhaps you just have some light feeders on your hands or your soil may already have enough good stuff in it keeping them happy.
I use TNC's Cal/Mag @ 2ml per litre for normal feeds or if I have a fiend on my hands she gets fed 4ml cal/mag.
If you want to keep it as organic as possible, dry and crush (in a low oven for 5 minutes) a few eggshells. I use 3-4 shells in a 10 litre pot. Poke some holes in the soil, say 4-5 deep holes with a chopstick, and refill them with the shells. Water it in and within a week you'll see the calcium deficiency start to fade away.
For Magnesium, add 1 teaspoon of molasses/black treacle to your water and feed them with that. Lots of good stuff in molasses to keep the plants and soil happy. Also a great thing to increase resin production :)
But yeah, if they're growing well without any additional nutrients then I'd carry on. No need to piss them off if they're growing happily :)