The phrase "slightly poor" is correct and usable in written English.
You can use it to describe something that is not extremely poor, but not great either, such as "His performance was slightly poor."
But that's sub judice, and probably in slightly poor taste.
After the training, managers decreased their initial assessment of themselves by 28.8%, from "slightly good" to "slightly poor". This change was corroborated by managers' peers, who reduced their assessment by 18.4%, from "slightly good" to "neither good nor bad," when looking back at their original observations of others.
If I'm honest, it still seems a slightly poor quality final.
Further increasing the concentration of DES leaded to a slightly poor optical purity of product (92% at 3 h).
These defect states probably act as amorphous centers and as results, the as-grown structures exhibit slightly poor crystallinity.
The uniformity of distribution of SiC particulates is better as compared to that of Figure 1a and slightly poor as compared to that of Figure 1b.
At nominal focus this results in slightly poorer spectral resolution for wavelengths > 50 Å.
For disrupted rock fall and slides, CAMEL's performance was slightly poorer.
The workers were rehired on slightly poorer conditions than before, with the exception of union members.
Model performance was improved by autologistic regression, and models restricted to widely available data were only slightly poorer.
(2) The bond-quality of SFCBs and BFRPs reinforcements proved slightly poorer than that of the steel bars.
