Water foaming in overflow and sump

My tank is a 110gallon with approx 20 gallons in my 30 gallon sump, about 9 months old from stabilization of water quality after cycle. Yesterday i performed my weekly 15% water change, nothing beyond the usual RO/DI 20 gallons with SG of 1.024 using Instant Ocean Reef crystals. Two weeks ago I switched from using Instant Ocean Salt with dosing of vitamins and trace elements for the fact that I am doing weekly water changes with better salt to replenish the used up elements. I would have thought that if it would be the salt change that it would have been something like the foam when I switched a day or two from the change to reef crystals. I am only seeing foam in the overflow box (which is about 3-4" full of water with a foam pre-filter that i swap and clean every other day) and in the sump where bio-balls used to be (took bio-balls out when i realized they were a nitrate factory) only eggcrate remains. I clean my skimmer cup about every 4 days and clean the return filter foam and the foam filter from the overflow into the sump about every 4 days. Seeing foam makes me uneasy and just want to make sure it's just me being over-cautious. Stock and contents of tank include:

Livestock
1 Foxface Lo
1 ORA Ocellaris Clown
4 Green Chromis
1 Lawnmower Blenny
1 Regal Tang
1 Copperband Butterfly
4-5 Turbo Snails
8 Red Legged Hermits
1 Queen Conch

Corals
<u>Softies</u>
Pulsing Xenia
Waving Hand Anthelias
GSP
Encrusting Gorgonian
Misc Zoas and Palys
Mushrooms

<u>LPS</u>
Branching Hammer Purpletip
Candy Cane

<u>SPS</u>
Acroporas
Montiporas
and 2 that i cannot remember name of but fairly young frags.

Water parameters are:
Calcium 430 ppm
Alkalinity 8 dKH
SG 1.024
PH 8.2
Temp 79 at night 80 daytime with lights
Magnesium 1270 ppm
Phosphate 0
Ammonia 0
Nitrite 0
Nitrate 0.1ppm (struggling to keep low with sand/crushed coral mix, planning on doing slow substrate change over a month. Beginner mistake that I'm paying for now)

Please let me know if foam in overflow and sump is normal after switching salts 2 weeks prior or if I may have an underlying problem that hasnt surfaced yet. Have only lost a diamond goby about 2 months ago swapping him from my 55g to my 110.
 
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