hypos

If it keeps up like that then you need to adjust your ratio for your lunch.......

timing could be an issue too......your meals may take longer to digest at that time of day so you need to play about with your bolus timing...

It is not unheard of to need different ratios at different times of the day.
For example, due to the Dawn Phenomenon, we may be slightly insulin resistant at breakfast time so need more insulin for the same amount of carbs. Many pump users have their pumps set up this way.
The advantage of a pump is that it takes care of all of this but, if you have to do your own calculation, it gets a bit complex when on injections so, usually, it's all simplified: same amount of basal all day every day and same ratio all day every day.
There are some meters available which allow you to program different ratios and let it do all the calculations. I tried one of these for a short while but, personally, felt I spent far too long pressing buttons to enter my carbs and wait for it to do the calculations that I gave up. But my ratios were pretty straightforward so I could just do arithmetic in my head.
Anyway, I digress slightly.
It may be worthwhile trying a slightly different ratio for lunch with less insulin and see how that works ... if you can bear to do the calculations.

Due to the Libre have you tweaked you breakfast dose? and now finding your numbers more stable and now for lunch you're starting on a better number which is now causing the post lunch lows? Agree with whats already been said that your lunch time ratio now may well have changed and also perhaps the timing of the bolus needs looking at - are you finding your BG is going really high after the post lunch time dip? (due to a combination of the quick acting correction carbs and the delayed carb absorption from lunch)

I have no clue about ratio's, but I do know I need a lot more insulin for the first carbs of the day than I need for subsequent carbs.