Corpeswade and Poisonous Concoction lag

I have been leveling with a low level 18 Corpeswade Iron Boots and Poisonous Concoction the skill goes grey, at least every hour or so and at times ten minutes apart I get lag or skill blocking where I cannot cast Poisonous Concoction and my Minions just look to be doing nothing.
I don't think I'm spamming the skills so It's not that, plus the skill uses next to no mana.

Please Delete this I worked it out, I was out of mana flash charges.