I have an eshopps on my 75, make sure the inside cone doesnt have filth built up on it (not the collection cup but actually the inside of the main cone/tube)
Every once and a while, it won't skim as much as it normally does and 9 times out of 10, its because I have filth build up on the inside of the skimmer that prevents the bubbles from rising and causes the excess filth and waste to build up on the inside. I use a brush (toothbrush will work) and scrub the inside of it best I can. Should work fine afterwards. Make sure to also dial it in, I found with the eshopps you want the bubble level to come up to the base of the collection cup for it to work efficiently.