Perils of c/u with general purpose lens! Unexpected extension tube results

I have been doing my "macro" photos with the Oly 40-150 + Raynox c/u lens or the Panny 45-150 + Raynox c/u lens with very pleasing results.

Recently, I also bought a Marumi 200 (+5) c/u lens for the Panny 12-35 -- again it looks good.

But recently, on the advice of people on this forum (you know who you are!!!) I bought a pair of Fotga extension tubes, one 10mm the other 16mm, giving a total of 26mm when required. Well made, they allow me to retain all automatic functions.

Initial testing showed I could use the two rings together behind the 454-150 and one of them max behind the 12-35 (it gets too close with two).

My thinking: lenses are designed to work on certain whys; introduce another piece of glass in front of them and you can scramble the formula. So far, I had got good results with the quality Raynox supplementary lenses (the 250 initially; the 150 currently), but results must be better if the glass is left unimpeded with merely an extension tube stuck on the back.

WRONG it turns out. Lenses are also designed to work within a focus range and this bit me on the b*m this morning when sallied forth in autumn sunshine in Melbourne (and about time; the last few days have been disgusting) to give the new GX7 a bit of a run.

With 26mm of extension tube behind the 45-150, I snapped the little white flowers on the hedge outside, then ventured down the road to where a neighbor had planted some little roses.

Came up well, didn't it?

But wait -- that was after heart stopping (for me!) PP in PhotoLine and PTLens plug-in to get rid of the nasties you can see here:

Whaaat? I have never seen that in c/u with the 45-150 before! But there it was in every pic the moment I looked a little away from the center.

I tried an as-near-as-I-could comparison with the 100-300 with the extension tubes behind it. No problems. (Yes, I know there is a fair bit of difference between the two circumstances, but I am not testing any further -- you can if you like!)

Then the 12-35 with the Maruni lens on the front (this is no comparison at all, really, but I had ti on hand to take a pic):

Since I have taken scores, perhaps hundreds of C/Us with the 45-150 + Raynox 150 on the front, I don't need to do a comparison test of that combination. I know it is fine.

SO it looks as though the 45-150 is sensitive in the lens-sensor distance. Perfectly reasonable and no criticism of the lens which works fine in its normal mode. It is just a bit of a nuisance for me. So it looks as though the extension tubes are for the high jump. A pity, but there it is. A flop-a-roo. And I have seen such nice pix other people have taken with them (you still know who you are -- come out from behind the sofa, Jaly et al, I am not about to abuse you! LOL!).