What are these on my onion leaves?

Hi all,

Noticed my onions growth has slowed quite a bit the last week and on inspection there are those tiny little insects on the leaves. They don't look like thrips I don't think. Any ideas? Hard to see as my phone camera kept going blurry when I got closer but it's the small light brown/gold things scattered all over the leaves. Moving about like tiny tiny spiders.

 

Surely not Red Spider Mite.
Where are they growing?

 

They are in my greenhouse. Growing in 40litre buckets sat on a raised bed. Used all fresh compost when I put them out. Only other thing growing in the greenhouse is some tomatoes but no signs of the insects on them.

 

They need to be outside.
It looks a bit like RSM to me, its nothing to do with the compost its the growing conditions.
Too hot and dry.

 

I'm growing giant onions for competition, always do half a dozen in the greenhouse for the heaviest onion class without any problems.

From the Google images of RSM the ones on mine don't look anywhere near as red as those.

What's the best solution for getting rid of these?

 

put the plants outside.

RSM are not actually red, more kind of yellow with usually two black spots on the back, you need a lense to see that, well I do anyway

Humidity is supposed to suppress them, but it's never worked for me on more tropical plants.